As a method for removing a target compound from drainage in drainage treatment, a method of combustion treatment or a method of biological treatment with a target compound-degrading microorganism or the like is used. As a method for obtaining a target compound-degrading microorganism, a method (a method of isolation culture) involving enrichment culture of microorganisms that degrade target compounds and identification, isolation, and pure culture the degrading microorganism is known. For mixed microorganism systems such as activated sludge, a method called acclimatization (a method of acclimatization) involving acclimating activated sludge to a target compound and increase its degradation capability by providing the target compound at a low concentration as a nutrition source and gradually increasing the concentration is known.
However, there is a problem in the method of isolation culture that it requires a long period of time for isolation of a degrading microorganism, suitable microorganisms are limited to those that can be cultured artificially, and production cost for pure culture is high. Meanwhile, the method of acclimatization allows culturing a degrading microorganism at low cost and in large quantities but there is a problem that a long period of time is required for the acclimatization.
Among other methods for making a target compound degrading microorganism high density, for example, a method for producing a microbiologic agent by making a nitrifying bacterium high density and aggregating microparticle solids and the microorganism into granules, having excellent physical properties is disclosed, as described in Patent Literature 1. This microbiologic agent is useful in effective treatment of drainage since it can be produced efficiently by continuous culture and also stored.